In a mixed mail transport system, a vertical stack mixed mail feeder, or stack advance, is used to support and advance the mail stack to a nudger. The nudger typically moves the individual mailpieces from the mail stack in a shingled manner toward a mail separator which separates individual pieces of mail for subsequent processing such as being canceled by a print head. A typical stack advance is shown in FIG. 1. In the stack advance 10, mailpieces 12 are loaded in a stack 14 upside down on a long deck 16, with the face 18 of the mailpieces facing the nudger (not shown), which is located near the downstream end 200 of the stack advance 10. The upstream end of the stack advance 10 is denoted by reference numeral 202. Perpendicular to the deck 16, a vertical registration wall 20 is used to register the mailpieces 12. In proper registration, the leading edge 22 of every mailpiece 12 in the stack is aligned against the registration wall 20. The bottom edges 24 of the mailpieces 12 are supported by a transport timing belt 30 and an outboard slider bed 34. An inboard slider bed, which is not shown in the figure, is located below the timing belt 30 for supporting the timing belt 30. The outboard slider bed 34 is provided on the trailing edge side 26 of the mailpieces 12 to allow the mailpieces 12 to slide toward the nudger along a direction indicated by an arrow 204. The timing belt 30, driven by a motor (not shown), is used to drive the mail stack 14 toward the nudger. The downstream side of the mail stack 14 is supported by a paddle 40. The bottom 42 of the paddle 44 has a paddle tooth (not shown) attached thereto for riding in the grooves 32 of the timing belt 30 for advancing the paddle 40 toward the downstream end 200 along with the mail stack 14. It should be noted that FIG. 1 shows only a few mailpieces 12 in a mail stack 14 being stacked on the stack advance 10. Typically, a mail stack fills the gap between the paddle 40 and the nudger. At the nudger, the leading edge 22 of each mailpiece 12 is ingested into the nudger along a direction indicated by an arrow 206. The mailpieces 12 from the stack 14 are separated by the nudger for further processing such as being canceled by a printhead (not shown).
Testing with vertical stack mixed mail feeders has shown that when mail is poorly registered onto the stack advance deck, the performance of the system, in terms of jams, stalls and multifeeds, degrades significantly. Furthermore, the quality of loading plays a great role in the performance of the vertical stack mixed mail feeders. When mail is poorly bottom registered, mail has a tendency to miss some or all of the driving and/or retard elements in the feeder. This will cause jams, stalls and multifeeds. When mail is poorly lead-edge registered, gross reverse shingling can occur, which greatly increases the likelihood of multifeeds. Therefore, to allow the machine to perform as well as possible, the mail must be bottom and lead-edge registered. Registering the mail manually is time-consuming, especially when the mail mix is severe. In an actual environment, it is impractical to rely on the operator to perform this difficult and time-consuming task.
It is, therefore, desirable to provide a method and device to improve the mail registration in a mixed mail feeder.